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<title>Flags (GNU Compiler Collection (GCC) Internals)</title>

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<h3 class="section" id="Flags-in-an-RTL-Expression"><span>14.5 Flags in an RTL Expression<a class="copiable-link" href="#Flags-in-an-RTL-Expression"> &para;</a></span></h3>
<a class="index-entry-id" id="index-flags-in-RTL-expression"></a>

<p>RTL expressions contain several flags (one-bit bit-fields)
that are used in certain types of expression.  Most often they
are accessed with the following macros, which expand into lvalues.
</p>
<dl class="table">
<dt><a class="index-entry-id" id="index-jump_005finsn-and-_002fj"></a>
<a id="index-CROSSING_005fJUMP_005fP"></a><span><code class="code">CROSSING_JUMP_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-CROSSING_005fJUMP_005fP"> &para;</a></span></dt>
<dd><p>Nonzero in a <code class="code">jump_insn</code> if it crosses between hot and cold sections,
which could potentially be very far apart in the executable.  The presence
of this flag indicates to other optimizations that this branching instruction
should not be &ldquo;collapsed&rdquo; into a simpler branching construct.  It is used
when the optimization to partition basic blocks into hot and cold sections
is turned on.
</p>
</dd>
<dt><a class="index-entry-id" id="index-symbol_005fref-and-_002fu"></a>
<a class="index-entry-id" id="index-unchanging_002c-in-symbol_005fref"></a>
<a id="index-CONSTANT_005fPOOL_005fADDRESS_005fP"></a><span><code class="code">CONSTANT_POOL_ADDRESS_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-CONSTANT_005fPOOL_005fADDRESS_005fP"> &para;</a></span></dt>
<dd><p>Nonzero in a <code class="code">symbol_ref</code> if it refers to part of the current
function&rsquo;s constant pool.  For most targets these addresses are in a
<code class="code">.rodata</code> section entirely separate from the function, but for
some targets the addresses are close to the beginning of the function.
In either case GCC assumes these addresses can be addressed directly,
perhaps with the help of base registers.
Stored in the <code class="code">unchanging</code> field and printed as &lsquo;<samp class="samp">/u</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-jump_005finsn-and-_002fu"></a>
<a class="index-entry-id" id="index-call_005finsn-and-_002fu"></a>
<a class="index-entry-id" id="index-insn-and-_002fu"></a>
<a class="index-entry-id" id="index-unchanging_002c-in-jump_005finsn_002c-call_005finsn-and-insn"></a>
<a id="index-INSN_005fANNULLED_005fBRANCH_005fP"></a><span><code class="code">INSN_ANNULLED_BRANCH_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-INSN_005fANNULLED_005fBRANCH_005fP"> &para;</a></span></dt>
<dd><p>In a <code class="code">jump_insn</code>, <code class="code">call_insn</code>, or <code class="code">insn</code> indicates
that the branch is an annulling one.  See the discussion under
<code class="code">sequence</code> below.  Stored in the <code class="code">unchanging</code> field and
printed as &lsquo;<samp class="samp">/u</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-insn-and-_002fv"></a>
<a class="index-entry-id" id="index-call_005finsn-and-_002fv"></a>
<a class="index-entry-id" id="index-jump_005finsn-and-_002fv"></a>
<a class="index-entry-id" id="index-code_005flabel-and-_002fv"></a>
<a class="index-entry-id" id="index-jump_005ftable_005fdata-and-_002fv"></a>
<a class="index-entry-id" id="index-barrier-and-_002fv"></a>
<a class="index-entry-id" id="index-note-and-_002fv"></a>
<a class="index-entry-id" id="index-volatil_002c-in-insn_002c-call_005finsn_002c-jump_005finsn_002c-code_005flabel_002c-jump_005ftable_005fdata_002c-barrier_002c-and-note"></a>
<a id="index-INSN_005fDELETED_005fP"></a><span><code class="code">INSN_DELETED_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-INSN_005fDELETED_005fP"> &para;</a></span></dt>
<dd><p>In an <code class="code">insn</code>, <code class="code">call_insn</code>, <code class="code">jump_insn</code>, <code class="code">code_label</code>,
<code class="code">jump_table_data</code>, <code class="code">barrier</code>, or <code class="code">note</code>,
nonzero if the insn has been deleted.  Stored in the
<code class="code">volatil</code> field and printed as &lsquo;<samp class="samp">/v</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-insn-and-_002fs"></a>
<a class="index-entry-id" id="index-jump_005finsn-and-_002fs"></a>
<a class="index-entry-id" id="index-call_005finsn-and-_002fs"></a>
<a class="index-entry-id" id="index-in_005fstruct_002c-in-insn-and-jump_005finsn-and-call_005finsn"></a>
<a id="index-INSN_005fFROM_005fTARGET_005fP"></a><span><code class="code">INSN_FROM_TARGET_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-INSN_005fFROM_005fTARGET_005fP"> &para;</a></span></dt>
<dd><p>In an <code class="code">insn</code> or <code class="code">jump_insn</code> or <code class="code">call_insn</code> in a delay
slot of a branch, indicates that the insn
is from the target of the branch.  If the branch insn has
<code class="code">INSN_ANNULLED_BRANCH_P</code> set, this insn will only be executed if
the branch is taken.  For annulled branches with
<code class="code">INSN_FROM_TARGET_P</code> clear, the insn will be executed only if the
branch is not taken.  When <code class="code">INSN_ANNULLED_BRANCH_P</code> is not set,
this insn will always be executed.  Stored in the <code class="code">in_struct</code>
field and printed as &lsquo;<samp class="samp">/s</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-code_005flabel-and-_002fi"></a>
<a class="index-entry-id" id="index-note-and-_002fi"></a>
<a class="index-entry-id" id="index-in_005fstruct_002c-in-code_005flabel-and-note"></a>
<a id="index-LABEL_005fPRESERVE_005fP"></a><span><code class="code">LABEL_PRESERVE_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-LABEL_005fPRESERVE_005fP"> &para;</a></span></dt>
<dd><p>In a <code class="code">code_label</code> or <code class="code">note</code>, indicates that the label is referenced by
code or data not visible to the RTL of a given function.
Labels referenced by a non-local goto will have this bit set.  Stored
in the <code class="code">in_struct</code> field and printed as &lsquo;<samp class="samp">/s</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-label_005fref-and-_002fv"></a>
<a class="index-entry-id" id="index-reg_005flabel-and-_002fv"></a>
<a class="index-entry-id" id="index-volatil_002c-in-label_005fref-and-reg_005flabel"></a>
<a id="index-LABEL_005fREF_005fNONLOCAL_005fP"></a><span><code class="code">LABEL_REF_NONLOCAL_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-LABEL_005fREF_005fNONLOCAL_005fP"> &para;</a></span></dt>
<dd><p>In <code class="code">label_ref</code> and <code class="code">reg_label</code> expressions, nonzero if this is
a reference to a non-local label.
Stored in the <code class="code">volatil</code> field and printed as &lsquo;<samp class="samp">/v</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-mem-and-_002fj"></a>
<a class="index-entry-id" id="index-jump_002c-in-mem"></a>
<a id="index-MEM_005fKEEP_005fALIAS_005fSET_005fP"></a><span><code class="code">MEM_KEEP_ALIAS_SET_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-MEM_005fKEEP_005fALIAS_005fSET_005fP"> &para;</a></span></dt>
<dd><p>In <code class="code">mem</code> expressions, 1 if we should keep the alias set for this
mem unchanged when we access a component.  Set to 1, for example, when we
are already in a non-addressable component of an aggregate.
Stored in the <code class="code">jump</code> field and printed as &lsquo;<samp class="samp">/j</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-mem-and-_002fv"></a>
<a class="index-entry-id" id="index-asm_005finput-and-_002fv"></a>
<a class="index-entry-id" id="index-asm_005foperands-and-_002fv"></a>
<a class="index-entry-id" id="index-volatil_002c-in-mem_002c-asm_005foperands_002c-and-asm_005finput"></a>
<a id="index-MEM_005fVOLATILE_005fP"></a><span><code class="code">MEM_VOLATILE_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-MEM_005fVOLATILE_005fP"> &para;</a></span></dt>
<dd><p>In <code class="code">mem</code>, <code class="code">asm_operands</code>, and <code class="code">asm_input</code> expressions,
nonzero for volatile memory references.
Stored in the <code class="code">volatil</code> field and printed as &lsquo;<samp class="samp">/v</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-mem-and-_002fc"></a>
<a class="index-entry-id" id="index-call_002c-in-mem"></a>
<a id="index-MEM_005fNOTRAP_005fP"></a><span><code class="code">MEM_NOTRAP_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-MEM_005fNOTRAP_005fP"> &para;</a></span></dt>
<dd><p>In <code class="code">mem</code>, nonzero for memory references that will not trap.
Stored in the <code class="code">call</code> field and printed as &lsquo;<samp class="samp">/c</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-mem-and-_002ff"></a>
<a class="index-entry-id" id="index-frame_005frelated_002c-in-mem"></a>
<a id="index-MEM_005fPOINTER"></a><span><code class="code">MEM_POINTER (<var class="var">x</var>)</code><a class="copiable-link" href="#index-MEM_005fPOINTER"> &para;</a></span></dt>
<dd><p>Nonzero in a <code class="code">mem</code> if the memory reference holds a pointer.
Stored in the <code class="code">frame_related</code> field and printed as &lsquo;<samp class="samp">/f</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-mem-and-_002fu"></a>
<a class="index-entry-id" id="index-unchanging_002c-in-mem"></a>
<a id="index-MEM_005fREADONLY_005fP"></a><span><code class="code">MEM_READONLY_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-MEM_005fREADONLY_005fP"> &para;</a></span></dt>
<dd><p>Nonzero in a <code class="code">mem</code>, if the memory is statically allocated and read-only.
</p>
<p>Read-only in this context means never modified during the lifetime of the
program, not necessarily in ROM or in write-disabled pages.  A common
example of the later is a shared library&rsquo;s global offset table.  This
table is initialized by the runtime loader, so the memory is technically
writable, but after control is transferred from the runtime loader to the
application, this memory will never be subsequently modified.
</p>
<p>Stored in the <code class="code">unchanging</code> field and printed as &lsquo;<samp class="samp">/u</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-prefetch-and-_002fv"></a>
<a class="index-entry-id" id="index-volatile_002c-in-prefetch"></a>
<a id="index-PREFETCH_005fSCHEDULE_005fBARRIER_005fP"></a><span><code class="code">PREFETCH_SCHEDULE_BARRIER_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-PREFETCH_005fSCHEDULE_005fBARRIER_005fP"> &para;</a></span></dt>
<dd><p>In a <code class="code">prefetch</code>, indicates that the prefetch is a scheduling barrier.
No other INSNs will be moved over it.
Stored in the <code class="code">volatil</code> field and printed as &lsquo;<samp class="samp">/v</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-reg-and-_002fi"></a>
<a class="index-entry-id" id="index-return_005fval_002c-in-reg"></a>
<a id="index-REG_005fFUNCTION_005fVALUE_005fP"></a><span><code class="code">REG_FUNCTION_VALUE_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-REG_005fFUNCTION_005fVALUE_005fP"> &para;</a></span></dt>
<dd><p>Nonzero in a <code class="code">reg</code> if it is the place in which this function&rsquo;s
value is going to be returned.  (This happens only in a hard
register.)  Stored in the <code class="code">return_val</code> field and printed as
&lsquo;<samp class="samp">/i</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-reg-and-_002ff"></a>
<a class="index-entry-id" id="index-frame_005frelated_002c-in-reg"></a>
<a id="index-REG_005fPOINTER"></a><span><code class="code">REG_POINTER (<var class="var">x</var>)</code><a class="copiable-link" href="#index-REG_005fPOINTER"> &para;</a></span></dt>
<dd><p>Nonzero in a <code class="code">reg</code> if the register holds a pointer.  Stored in the
<code class="code">frame_related</code> field and printed as &lsquo;<samp class="samp">/f</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-reg-and-_002fv"></a>
<a class="index-entry-id" id="index-volatil_002c-in-reg"></a>
<a id="index-REG_005fUSERVAR_005fP"></a><span><code class="code">REG_USERVAR_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-REG_005fUSERVAR_005fP"> &para;</a></span></dt>
<dd><p>In a <code class="code">reg</code>, nonzero if it corresponds to a variable present in
the user&rsquo;s source code.  Zero for temporaries generated internally by
the compiler.  Stored in the <code class="code">volatil</code> field and printed as
&lsquo;<samp class="samp">/v</samp>&rsquo;.
</p>
<p>The same hard register may be used also for collecting the values of
functions called by this one, but <code class="code">REG_FUNCTION_VALUE_P</code> is zero
in this kind of use.
</p>
</dd>
<dt><a class="index-entry-id" id="index-call_005finsn-and-_002fu-1"></a>
<a class="index-entry-id" id="index-unchanging_002c-in-call_005finsn"></a>
<a id="index-RTL_005fCONST_005fCALL_005fP"></a><span><code class="code">RTL_CONST_CALL_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-RTL_005fCONST_005fCALL_005fP"> &para;</a></span></dt>
<dd><p>In a <code class="code">call_insn</code> indicates that the insn represents a call to a
const function.  Stored in the <code class="code">unchanging</code> field and printed as
&lsquo;<samp class="samp">/u</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-call_005finsn-and-_002fi"></a>
<a class="index-entry-id" id="index-return_005fval_002c-in-call_005finsn"></a>
<a id="index-RTL_005fPURE_005fCALL_005fP"></a><span><code class="code">RTL_PURE_CALL_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-RTL_005fPURE_005fCALL_005fP"> &para;</a></span></dt>
<dd><p>In a <code class="code">call_insn</code> indicates that the insn represents a call to a
pure function.  Stored in the <code class="code">return_val</code> field and printed as
&lsquo;<samp class="samp">/i</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-call_005finsn-and-_002fu-or-_002fi"></a>
<a id="index-RTL_005fCONST_005fOR_005fPURE_005fCALL_005fP"></a><span><code class="code">RTL_CONST_OR_PURE_CALL_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-RTL_005fCONST_005fOR_005fPURE_005fCALL_005fP"> &para;</a></span></dt>
<dd><p>In a <code class="code">call_insn</code>, true if <code class="code">RTL_CONST_CALL_P</code> or
<code class="code">RTL_PURE_CALL_P</code> is true.
</p>
</dd>
<dt><a class="index-entry-id" id="index-call_005finsn-and-_002fc"></a>
<a class="index-entry-id" id="index-call_002c-in-call_005finsn"></a>
<a id="index-RTL_005fLOOPING_005fCONST_005fOR_005fPURE_005fCALL_005fP"></a><span><code class="code">RTL_LOOPING_CONST_OR_PURE_CALL_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-RTL_005fLOOPING_005fCONST_005fOR_005fPURE_005fCALL_005fP"> &para;</a></span></dt>
<dd><p>In a <code class="code">call_insn</code> indicates that the insn represents a possibly
infinite looping call to a const or pure function.  Stored in the
<code class="code">call</code> field and printed as &lsquo;<samp class="samp">/c</samp>&rsquo;.  Only true if one of
<code class="code">RTL_CONST_CALL_P</code> or <code class="code">RTL_PURE_CALL_P</code> is true.
</p>
</dd>
<dt><a class="index-entry-id" id="index-insn-and-_002ff"></a>
<a class="index-entry-id" id="index-call_005finsn-and-_002ff"></a>
<a class="index-entry-id" id="index-jump_005finsn-and-_002ff"></a>
<a class="index-entry-id" id="index-barrier-and-_002ff"></a>
<a class="index-entry-id" id="index-set-and-_002ff"></a>
<a class="index-entry-id" id="index-frame_005frelated_002c-in-insn_002c-call_005finsn_002c-jump_005finsn_002c-barrier_002c-and-set"></a>
<a id="index-RTX_005fFRAME_005fRELATED_005fP"></a><span><code class="code">RTX_FRAME_RELATED_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-RTX_005fFRAME_005fRELATED_005fP"> &para;</a></span></dt>
<dd><p>Nonzero in an <code class="code">insn</code>, <code class="code">call_insn</code>, <code class="code">jump_insn</code>,
<code class="code">barrier</code>, or <code class="code">set</code> which is part of a function prologue
and sets the stack pointer, sets the frame pointer, or saves a register.
This flag should also be set on an instruction that sets up a temporary
register to use in place of the frame pointer.
Stored in the <code class="code">frame_related</code> field and printed as &lsquo;<samp class="samp">/f</samp>&rsquo;.
</p>
<p>In particular, on RISC targets where there are limits on the sizes of
immediate constants, it is sometimes impossible to reach the register
save area directly from the stack pointer.  In that case, a temporary
register is used that is near enough to the register save area, and the
Canonical Frame Address, i.e., DWARF2&rsquo;s logical frame pointer, register
must (temporarily) be changed to be this temporary register.  So, the
instruction that sets this temporary register must be marked as
<code class="code">RTX_FRAME_RELATED_P</code>.
</p>
<p>If the marked instruction is overly complex (defined in terms of what
<code class="code">dwarf2out_frame_debug_expr</code> can handle), you will also have to
create a <code class="code">REG_FRAME_RELATED_EXPR</code> note and attach it to the
instruction.  This note should contain a simple expression of the
computation performed by this instruction, i.e., one that
<code class="code">dwarf2out_frame_debug_expr</code> can handle.
</p>
<p>This flag is required for exception handling support on targets with RTL
prologues.
</p>
</dd>
<dt><a class="index-entry-id" id="index-insn-and-_002fs-1"></a>
<a class="index-entry-id" id="index-call_005finsn-and-_002fs-1"></a>
<a class="index-entry-id" id="index-jump_005finsn-and-_002fs-1"></a>
<a class="index-entry-id" id="index-jump_005ftable_005fdata-and-_002fs"></a>
<a class="index-entry-id" id="index-in_005fstruct_002c-in-insn_002c-call_005finsn_002c-jump_005finsn-and-jump_005ftable_005fdata"></a>
<a id="index-SCHED_005fGROUP_005fP"></a><span><code class="code">SCHED_GROUP_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-SCHED_005fGROUP_005fP"> &para;</a></span></dt>
<dd><p>During instruction scheduling, in an <code class="code">insn</code>, <code class="code">call_insn</code>,
<code class="code">jump_insn</code> or <code class="code">jump_table_data</code>, indicates that the
previous insn must be scheduled together with this insn.  This is used to
ensure that certain groups of instructions will not be split up by the
instruction scheduling pass, for example, <code class="code">use</code> insns before
a <code class="code">call_insn</code> may not be separated from the <code class="code">call_insn</code>.
Stored in the <code class="code">in_struct</code> field and printed as &lsquo;<samp class="samp">/s</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-insn-and-_002fj"></a>
<a class="index-entry-id" id="index-jump_002c-in-insn"></a>
<a id="index-SET_005fIS_005fRETURN_005fP"></a><span><code class="code">SET_IS_RETURN_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-SET_005fIS_005fRETURN_005fP"> &para;</a></span></dt>
<dd><p>For a <code class="code">set</code>, nonzero if it is for a return.
Stored in the <code class="code">jump</code> field and printed as &lsquo;<samp class="samp">/j</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-call_005finsn-and-_002fj"></a>
<a class="index-entry-id" id="index-jump_002c-in-call_005finsn"></a>
<a id="index-SIBLING_005fCALL_005fP"></a><span><code class="code">SIBLING_CALL_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-SIBLING_005fCALL_005fP"> &para;</a></span></dt>
<dd><p>For a <code class="code">call_insn</code>, nonzero if the insn is a sibling call.
Stored in the <code class="code">jump</code> field and printed as &lsquo;<samp class="samp">/j</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-symbol_005fref-and-_002ff"></a>
<a class="index-entry-id" id="index-frame_005frelated_002c-in-symbol_005fref"></a>
<a id="index-STRING_005fPOOL_005fADDRESS_005fP"></a><span><code class="code">STRING_POOL_ADDRESS_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-STRING_005fPOOL_005fADDRESS_005fP"> &para;</a></span></dt>
<dd><p>For a <code class="code">symbol_ref</code> expression, nonzero if it addresses this function&rsquo;s
string constant pool.
Stored in the <code class="code">frame_related</code> field and printed as &lsquo;<samp class="samp">/f</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-subreg-and-_002fu-and-_002fv"></a>
<a class="index-entry-id" id="index-unchanging_002c-in-subreg"></a>
<a class="index-entry-id" id="index-volatil_002c-in-subreg"></a>
<a id="index-SUBREG_005fPROMOTED_005fUNSIGNED_005fP"></a><span><code class="code">SUBREG_PROMOTED_UNSIGNED_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-SUBREG_005fPROMOTED_005fUNSIGNED_005fP"> &para;</a></span></dt>
<dd><p>Returns a value greater then zero for a <code class="code">subreg</code> that has
<code class="code">SUBREG_PROMOTED_VAR_P</code> nonzero if the object being referenced is kept
zero-extended, zero if it is kept sign-extended, and less then zero if it is
extended some other way via the <code class="code">ptr_extend</code> instruction.
Stored in the <code class="code">unchanging</code>
field and <code class="code">volatil</code> field, printed as &lsquo;<samp class="samp">/u</samp>&rsquo; and &lsquo;<samp class="samp">/v</samp>&rsquo;.
This macro may only be used to get the value it may not be used to change
the value.  Use <code class="code">SUBREG_PROMOTED_UNSIGNED_SET</code> to change the value.
</p>
</dd>
<dt><a class="index-entry-id" id="index-subreg-and-_002fu"></a>
<a class="index-entry-id" id="index-unchanging_002c-in-subreg-1"></a>
<a class="index-entry-id" id="index-volatil_002c-in-subreg-1"></a>
<a id="index-SUBREG_005fPROMOTED_005fUNSIGNED_005fSET"></a><span><code class="code">SUBREG_PROMOTED_UNSIGNED_SET (<var class="var">x</var>)</code><a class="copiable-link" href="#index-SUBREG_005fPROMOTED_005fUNSIGNED_005fSET"> &para;</a></span></dt>
<dd><p>Set the <code class="code">unchanging</code> and <code class="code">volatil</code> fields in a <code class="code">subreg</code>
to reflect zero, sign, or other extension.  If <code class="code">volatil</code> is
zero, then <code class="code">unchanging</code> as nonzero means zero extension and as
zero means sign extension.  If <code class="code">volatil</code> is nonzero then some
other type of extension was done via the <code class="code">ptr_extend</code> instruction.
</p>
</dd>
<dt><a class="index-entry-id" id="index-subreg-and-_002fs"></a>
<a class="index-entry-id" id="index-in_005fstruct_002c-in-subreg"></a>
<a id="index-SUBREG_005fPROMOTED_005fVAR_005fP"></a><span><code class="code">SUBREG_PROMOTED_VAR_P (<var class="var">x</var>)</code><a class="copiable-link" href="#index-SUBREG_005fPROMOTED_005fVAR_005fP"> &para;</a></span></dt>
<dd><p>Nonzero in a <code class="code">subreg</code> if it was made when accessing an object that
was promoted to a wider mode in accord with the <code class="code">PROMOTED_MODE</code> machine
description macro (see <a class="pxref" href="Storage-Layout.html">Storage Layout</a>).  In this case, the mode of
the <code class="code">subreg</code> is the declared mode of the object and the mode of
<code class="code">SUBREG_REG</code> is the mode of the register that holds the object.
Promoted variables are always either sign- or zero-extended to the wider
mode on every assignment.  Stored in the <code class="code">in_struct</code> field and
printed as &lsquo;<samp class="samp">/s</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-used_002c-in-symbol_005fref"></a>
<a id="index-SYMBOL_005fREF_005fUSED"></a><span><code class="code">SYMBOL_REF_USED (<var class="var">x</var>)</code><a class="copiable-link" href="#index-SYMBOL_005fREF_005fUSED"> &para;</a></span></dt>
<dd><p>In a <code class="code">symbol_ref</code>, indicates that <var class="var">x</var> has been used.  This is
normally only used to ensure that <var class="var">x</var> is only declared external
once.  Stored in the <code class="code">used</code> field.
</p>
</dd>
<dt><a class="index-entry-id" id="index-symbol_005fref-and-_002fi"></a>
<a class="index-entry-id" id="index-return_005fval_002c-in-symbol_005fref"></a>
<a id="index-SYMBOL_005fREF_005fWEAK"></a><span><code class="code">SYMBOL_REF_WEAK (<var class="var">x</var>)</code><a class="copiable-link" href="#index-SYMBOL_005fREF_005fWEAK"> &para;</a></span></dt>
<dd><p>In a <code class="code">symbol_ref</code>, indicates that <var class="var">x</var> has been declared weak.
Stored in the <code class="code">return_val</code> field and printed as &lsquo;<samp class="samp">/i</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-symbol_005fref-and-_002fv"></a>
<a class="index-entry-id" id="index-volatil_002c-in-symbol_005fref"></a>
<a id="index-SYMBOL_005fREF_005fFLAG"></a><span><code class="code">SYMBOL_REF_FLAG (<var class="var">x</var>)</code><a class="copiable-link" href="#index-SYMBOL_005fREF_005fFLAG"> &para;</a></span></dt>
<dd><p>In a <code class="code">symbol_ref</code>, this is used as a flag for machine-specific purposes.
Stored in the <code class="code">volatil</code> field and printed as &lsquo;<samp class="samp">/v</samp>&rsquo;.
</p>
<p>Most uses of <code class="code">SYMBOL_REF_FLAG</code> are historic and may be subsumed
by <code class="code">SYMBOL_REF_FLAGS</code>.  Certainly use of <code class="code">SYMBOL_REF_FLAGS</code>
is mandatory if the target requires more than one bit of storage.
</p></dd>
</dl>

<p>These are the fields to which the above macros refer:
</p>
<dl class="table">
<dt><a class="index-entry-id" id="index-_002fc-in-RTL-dump"></a>
<a id="index-call"></a><span><code class="code">call</code><a class="copiable-link" href="#index-call"> &para;</a></span></dt>
<dd><p>In a <code class="code">mem</code>, 1 means that the memory reference will not trap.
</p>
<p>In a <code class="code">call</code>, 1 means that this pure or const call may possibly
infinite loop.
</p>
<p>In an RTL dump, this flag is represented as &lsquo;<samp class="samp">/c</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-_002ff-in-RTL-dump"></a>
<a id="index-frame_005frelated"></a><span><code class="code">frame_related</code><a class="copiable-link" href="#index-frame_005frelated"> &para;</a></span></dt>
<dd><p>In an <code class="code">insn</code> or <code class="code">set</code> expression, 1 means that it is part of
a function prologue and sets the stack pointer, sets the frame pointer,
saves a register, or sets up a temporary register to use in place of the
frame pointer.
</p>
<p>In <code class="code">reg</code> expressions, 1 means that the register holds a pointer.
</p>
<p>In <code class="code">mem</code> expressions, 1 means that the memory reference holds a pointer.
</p>
<p>In <code class="code">symbol_ref</code> expressions, 1 means that the reference addresses
this function&rsquo;s string constant pool.
</p>
<p>In an RTL dump, this flag is represented as &lsquo;<samp class="samp">/f</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-_002fs-in-RTL-dump"></a>
<a id="index-in_005fstruct"></a><span><code class="code">in_struct</code><a class="copiable-link" href="#index-in_005fstruct"> &para;</a></span></dt>
<dd><p>In <code class="code">reg</code> expressions, it is 1 if the register has its entire life
contained within the test expression of some loop.
</p>
<p>In <code class="code">subreg</code> expressions, 1 means that the <code class="code">subreg</code> is accessing
an object that has had its mode promoted from a wider mode.
</p>
<p>In <code class="code">label_ref</code> expressions, 1 means that the referenced label is
outside the innermost loop containing the insn in which the <code class="code">label_ref</code>
was found.
</p>
<p>In <code class="code">code_label</code> expressions, it is 1 if the label may never be deleted.
This is used for labels which are the target of non-local gotos.  Such a
label that would have been deleted is replaced with a <code class="code">note</code> of type
<code class="code">NOTE_INSN_DELETED_LABEL</code>.
</p>
<p>In an <code class="code">insn</code> during dead-code elimination, 1 means that the insn is
dead code.
</p>
<p>In an <code class="code">insn</code> or <code class="code">jump_insn</code> during reorg for an insn in the
delay slot of a branch,
1 means that this insn is from the target of the branch.
</p>
<p>In an <code class="code">insn</code> during instruction scheduling, 1 means that this insn
must be scheduled as part of a group together with the previous insn.
</p>
<p>In an RTL dump, this flag is represented as &lsquo;<samp class="samp">/s</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-_002fi-in-RTL-dump"></a>
<a id="index-return_005fval"></a><span><code class="code">return_val</code><a class="copiable-link" href="#index-return_005fval"> &para;</a></span></dt>
<dd><p>In <code class="code">reg</code> expressions, 1 means the register contains
the value to be returned by the current function.  On
machines that pass parameters in registers, the same register number
may be used for parameters as well, but this flag is not set on such
uses.
</p>
<p>In <code class="code">symbol_ref</code> expressions, 1 means the referenced symbol is weak.
</p>
<p>In <code class="code">call</code> expressions, 1 means the call is pure.
</p>
<p>In an RTL dump, this flag is represented as &lsquo;<samp class="samp">/i</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-_002fj-in-RTL-dump"></a>
<a id="index-jump"></a><span><code class="code">jump</code><a class="copiable-link" href="#index-jump"> &para;</a></span></dt>
<dd><p>In a <code class="code">mem</code> expression, 1 means we should keep the alias set for this
mem unchanged when we access a component.
</p>
<p>In a <code class="code">set</code>, 1 means it is for a return.
</p>
<p>In a <code class="code">call_insn</code>, 1 means it is a sibling call.
</p>
<p>In a <code class="code">jump_insn</code>, 1 means it is a crossing jump.
</p>
<p>In an RTL dump, this flag is represented as &lsquo;<samp class="samp">/j</samp>&rsquo;.
</p>
</dd>
<dt><a class="index-entry-id" id="index-_002fu-in-RTL-dump"></a>
<a id="index-unchanging"></a><span><code class="code">unchanging</code><a class="copiable-link" href="#index-unchanging"> &para;</a></span></dt>
<dd><p>In <code class="code">reg</code> and <code class="code">mem</code> expressions, 1 means
that the value of the expression never changes.
</p>
<p>In <code class="code">subreg</code> expressions, it is 1 if the <code class="code">subreg</code> references an
unsigned object whose mode has been promoted to a wider mode.
</p>
<p>In an <code class="code">insn</code> or <code class="code">jump_insn</code> in the delay slot of a branch
instruction, 1 means an annulling branch should be used.
</p>
<p>In a <code class="code">symbol_ref</code> expression, 1 means that this symbol addresses
something in the per-function constant pool.
</p>
<p>In a <code class="code">call_insn</code> 1 means that this instruction is a call to a const
function.
</p>
<p>In an RTL dump, this flag is represented as &lsquo;<samp class="samp">/u</samp>&rsquo;.
</p>
</dd>
<dt><a id="index-used"></a><span><code class="code">used</code><a class="copiable-link" href="#index-used"> &para;</a></span></dt>
<dd><p>This flag is used directly (without an access macro) at the end of RTL
generation for a function, to count the number of times an expression
appears in insns.  Expressions that appear more than once are copied,
according to the rules for shared structure (see <a class="pxref" href="Sharing.html">Structure Sharing Assumptions</a>).
</p>
<p>For a <code class="code">reg</code>, it is used directly (without an access macro) by the
leaf register renumbering code to ensure that each register is only
renumbered once.
</p>
<p>In a <code class="code">symbol_ref</code>, it indicates that an external declaration for
the symbol has already been written.
</p>
</dd>
<dt><a class="index-entry-id" id="index-_002fv-in-RTL-dump"></a>
<a class="index-entry-id" id="index-volatile-memory-references"></a>
<a id="index-volatil"></a><span><code class="code">volatil</code><a class="copiable-link" href="#index-volatil"> &para;</a></span></dt>
<dd><p>In a <code class="code">mem</code>, <code class="code">asm_operands</code>, or <code class="code">asm_input</code>
expression, it is 1 if the memory
reference is volatile.  Volatile memory references may not be deleted,
reordered or combined.
</p>
<p>In a <code class="code">symbol_ref</code> expression, it is used for machine-specific
purposes.
</p>
<p>In a <code class="code">reg</code> expression, it is 1 if the value is a user-level variable.
0 indicates an internal compiler temporary.
</p>
<p>In an <code class="code">insn</code>, 1 means the insn has been deleted.
</p>
<p>In <code class="code">label_ref</code> and <code class="code">reg_label</code> expressions, 1 means a reference
to a non-local label.
</p>
<p>In <code class="code">prefetch</code> expressions, 1 means that the containing insn is a
scheduling barrier.
</p>
<p>In an RTL dump, this flag is represented as &lsquo;<samp class="samp">/v</samp>&rsquo;.
</p></dd>
</dl>

</div>
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